当各种验证控件的验证类型都不能满足需要时可以使用CustomValidator验证控件，通过自定义验证函数来验证。直接看例子
<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="CustomValidator.aspx.cs" Inherits="WebApplication1.CustomValidator" %> <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"> <head runat="server"> <title></title> <style type ="text/css" > .red { color:Red ; } </style> <script type ="text/javascript" > function cvComment_ServerValidate(source, args) { if (args.Value.Length > 10) args.IsValid = false; else args.IsValid = true; } </script> </head> <body> <form id="form1" runat="server"> <div> <asp:ValidationSummary ID="ValidationSummary1" runat="server" ShowMessageBox ="true" ShowSummary ="true" /> <asp:Label runat ="server" Text ="comments:" AssociatedControlID ="txtComment"></asp:Label> <br /> <asp:TextBox ID ="txtComment" runat ="server" Rows ="5" Columns ="30" TextMode ="MultiLine" ></asp:TextBox> <asp:CustomValidator ID ="cvComment" runat ="server" ValidateEmptyText ="false" ControlToValidate ="txtComment" Text ="Comments must less than 10 characters" ErrorMessage ="Comments must less than 10 characters." Display ="Dynamic" CssClass ="red" onservervalidate="cvComment_ServerValidate" ClientValidationFunction="cvComment_ServerValidate" ></asp:CustomValidator> <asp:RequiredFieldValidator ID ="reqComment" runat ="server" Text ="(Required)" Display ="Dynamic" ErrorMessage ="Comments is required." CssClass ="red" ControlToValidate ="txtComment"></asp:RequiredFieldValidator> <br /> <asp:Button ID="btnSummit" runat="server" Text="Summit" /> <br /> </div> </form> </body> </html>
using System; using System.Collections.Generic; using System.Linq; using System.Web; using System.Web.UI; using System.Web.UI.WebControls; namespace WebApplication1 { public partial class CustomValidator : System.Web.UI.Page { protected void Page_Load(object sender, EventArgs e) { } protected void cvComment_ServerValidate(object source, ServerValidateEventArgs args) { if (args.Value.Length > 10) args.IsValid = false; else args.IsValid = true; } } }
通过在CustomValidator控件的servervalidate事件编写验证代码实现控件的服务器端验证。args.Value表示验证的表单字段的值，args.IsValid表示验证成功或者失败
ClientValidationFunction属性设置客户端验证脚本，服务器端事件处理函数和客户端脚本相同，不同的是使用的语言不一样。
ValidationSummary控件可以显示所有验证控件错误信息，ShowMessageBox表示是否弹窗，默认为false ;ShowSummary表示是否在页面中显示验证信息，比如设置了弹窗可以不在页面中再次显示错误信息可以设置ShowSummary='false'.
每个验证控件都有ErrorMessage、和Text两个属性，区别在于ErrorMessage用于在ValidationSummary显示，而Text在具体的验证控件中显示，所以一般情况下ErrorMessage要能识别有错误的表单字段，而Text字段一般要进来简短。
注意：CustomValidator有验证错误时并不像其他验证控件（如RequiredFieldValidator）一样阻止页面提交。
CustomValidator中的ControlToValidate并不是必须的，比如
<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="WebForm1.aspx.cs" Inherits="WebApplication1.WebForm1" %> <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"> <head runat="server"> <title></title> </head> <body> <form id="form1" runat="server"> <div> <p>你有5秒钟回答如下问题</p> <asp:Label ID="Label1" runat="server" Text="爱因斯坦是穿越者吗？"></asp:Label><br /> <asp:TextBox ID="txtAnswer" runat="server" Rows ="5" Columns ="30" TextMode ="MultiLine" ></asp:TextBox> <asp:CustomValidator runat ="server" Text ="你回答太慢了！" onservervalidate="Unnamed1_ServerValidate"></asp:CustomValidator> <br /> <asp:Button ID="btnSummit" runat="server" Text="Summit" /> </div> </form> </body> </html>
using System; using System.Collections.Generic; using System.Linq; using System.Web; using System.Web.UI; using System.Web.UI.WebControls; namespace WebApplication1 { public partial class WebForm1 : System.Web.UI.Page { protected void Page_Load(object sender, EventArgs e) { if(!IsPostBack) Session["startTime"] = DateTime.Now; } protected void Unnamed1_ServerValidate(object source, ServerValidateEventArgs args) { DateTime startTime =(DateTime)Session["startTime"]; if (startTime.AddSeconds(5) > DateTime.Now) args.IsValid = true; else args.IsValid = false; } } }